Vehicles may be fitted with evaporative emission systems such as onboard fuel vapor recovery systems. Such systems capture and prevent release of vaporized hydrocarbons to the atmosphere, for example fuel vapors generated in a vehicle gasoline tank during refueling. Specifically, the vaporized hydrocarbons (HCs) are stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors. At a later time, when the engine is in operation, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel. The fuel vapor recovery system may include one more check valves, ejectors (or venturis), and/or controller actuatable valves for facilitating purge of stored vapors under boosted or non-boosted engine operation. Specifically, ejectors may be coupled to the air induction system of the engine and the evaporative emissions system in order to generate vacuum when the intake manifold of the engine is pressurized (e.g., boosted due to operation of a compressor) and enable purging of fuel vapors from the fuel vapor canister to the air induction system. However, if such ejectors develop a leak or if one or more hoses or ducting coupled to the ejector becomes degraded, it may be possible for gases containing fuel vapors to escape to the atmosphere. Thus, these ejectors must either be diagnosable for correct operation (and prevention of fuel vapor leakage to the atmosphere) or the ejector nozzle must be located inside the air induction system. However, the inventors herein have recognized that positioning the ejector nozzle inside the air induction system limits engine packaging and increases costs.
Some approaches diagnose and detect leaks in ejector system components adjacent to the ejector inlets and/or upstream of the ejector inlets. For example, using a variety of sensors in an engine system, leaks may be detected in hoses, conduits, or ductwork coupled to the inlet of the ejector or at other locations in an ejector system upstream of the ejector outlet. However, such approaches fail to diagnose or detect leaks in an ejector system at or downstream of the ejector outlet. For example, a hose or other ducting may be used to couple the outlet of an ejector to an engine intake at a position upstream of a compressor. If such a hose degrades, or decouples from the ejector outlet, the resulting leak in the ejector system may remain undetected leading to increased emissions and degradation in engine operation.
Other attempts to address detecting ejector leaks and preventing fuel vapors from escaping to the atmosphere include hard-mounting the ejector to the air induction system and/or including one or more shut-off valves in the ejector. One example approach is shown by Euliss et al. in U.S. Pat. No. 9,243,595. Therein, an outlet of the ejector may be either hard-mounted to the air induction system or include one or more shut-off valves. The ejector may also include at least one break-point at the constriction or inlets of the ejector. Ejector failure at the break-points directs leaks away from the outlet to the inlets, where they may be detected without additional sensors or logic.
However, the inventors herein have recognized potential issues with such systems. As one example, hard-mounting the outlet to the air induction system may not result in a clear, detectable leak if the outlet connection becomes degraded or partially disconnected. Additionally, including one or more break-points may be complicated to implement, thereby increasing manufacturing costs of the ejector and/or still resulting in fuel vapor leakage to the atmosphere.
In one example, the issues described above may be addressed by a system, comprising: an air induction passage of an engine including an inlet flow port and an external protrusion having a closed end, each branching off a same side of the air induction passage; and an ejector, including: a constriction arranged between an outlet adapted to couple to the inlet flow port and an evacuation port adapted to couple to the protrusion; and first and second inlets positioned on either side of the constriction. In one example, the first inlet is coupled to an intake manifold of the engine, the second inlet is coupled to a fuel vapor canister of an evaporative emissions systems, and the outlet is coupled to the air induction passage, upstream of a compressor. During engine operation, if the outlet becomes uncoupled from the inlet flow port, the evacuation port may also become uncoupled from the external protrusion. As a result, the external protrusion will no longer block flow from exiting the ejector via the evacuation port and gases (e.g., compressed intake air from the intake manifold) flowing through the ejector will exit via the evacuation port before passing through the constriction. This may disable the vacuum generation at the constriction, thereby preventing fuel vapors from being pulled into the ejector via the second inlet. As a result, fuel vapors may not escape the ejector via the disconnected outlet of the ejector. In this way, the ejector may self-disable when becoming disconnected from the air induction system, thereby reducing the leakage of fuel vapors into the atmosphere. Further, by providing a self-disabling ejector, costly valve components and monitoring systems for detecting a disconnected ejector are not needed, thereby reducing engine control complexity and costs.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.